Heat sink



FIG. 1 is a front view of the heat sink, with a back view being the same;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right-side view thereof, with a left-side view being the same;

FIG. 4 is a bottom view thereof;

FIG. 5 is an enlarged partial view shown in FIG. 6, thereof;

FIG. 6 is a front view thereof; showing the section where FIG. 5 is taken within broken lines; and,

FIG. 7 is a top perspective view thereof.

The broken lines encircling a section of FIG. 6 are for indicating where the enlarged FIG. 5 view is taken and form no part of the claimed design. 

CLAIM The ornamental design for a heat sink, as shown and described. 